The present invention relates to dosing device for an inhaler and more particularly to an inhaler dosing device, during an inspiration for administering a pharmaceutical substance, providing a slower administration of the pharmaceutical substance to reach the deep areas of the lung of a patient.
Inhalers have been developed from being very simple to the up-to-date relatively complicated devices. For the up-to-date inhalers some form of mechanical dosing is almost entirely used for preparing the dose to be inhaled. Most often the dosing of the amount to be inhaled takes place industrially in advance in the form of a blister pack containing 10-50 doses. The inhaler then is loaded with this blister pack as the source of each dose. Other inhalers have a magazine from which the powder is dosed by some device for distribution to the inspiration air. In both cases the powder will generally be strongly agglomerated and therefore must be dispersed.
This dispersion of the agglomerates today mainly takes place by means of techniques in which the energy of the inspiration air is utilized. A normal inhalation takes place during about two seconds and a peaceful inspiration takes 3-4 seconds. In such designs, in which only the inhalation air is utilized for the de-agglomeration, only a fraction of the energy of the inhalation air will be utilized, as the dose of powder is given normally during only 0.1 to 0.4 s. Consequently this results in a low exploitation of the available energy which as a matter of fact will be present in the inhalation air. As only a small portion of the amount of energy is used it will be too low for a sufficient dispersion to take place. The total respirable dose therefore becomes very dependent on the occasion and the individual patient and thereby very varying from time to time. To improve this condition a number of inhalers include some kind of device against which the powder should collide and thereby transfer energy for de-agglomerating the powder.
However, such a collision with a fixed or mechanically moving object involves that a relatively large amount of powder sticks either permanently or is transported further together with the next dose. In both cases this constitutes a negative factor for the goal of obtaining a high accuracy and quality of the inhaled dose, e.g. an accurate amount of powder having a high portion of very small particles.
In a document WO97/00704 is described an inhaler device in which the substance to be administered is charged electrostatically and the dosing is performed by means of the assistance of a rotating dosing drum attracting the charged particles of the substance. The substance is then emitted from the dosing drum by means of a combination of an additional electric field and the air stream resulting from an inspiration. In advance of a desired dosing step the substance to be administered is kept in a reservoir, loaded for instance by means of receiving a cartridge containing the substance intended for many operations of the device.
There is still a demand for an inhaler device for inhaling a suitable medical substance, by means of which device the inhaled substance will be more even distributed during the entire inspiration than what is presented by inhalers according to the state of the art.
A dosing device of an inhaler for administering a pharmaceutical composition during a prolonged time period is disclosed. The powder to be administered is gathered as an extended dose or string of fine powder onto an envelope surface of a dosing member. The dosing member contains a number of prefabricated doses to be accessed. A dosing element having an adapted opening moves along the extended dose arrangement of the dosing member during the administration to in this manner prolong the time period, during which the pharmaceutical composition is released from the dosing member into an air-stream of the inhaler during an inspiration. This motion is either obtained by rotating the dosing member itself or moving the dosing element long the surface of the dosing member. Thereby an even distributed amount of very fine powder in the inspiration air is obtained during for instance one to two seconds of inspiration in accordance with the motion of the dosing element or the dosing member.